I wouldn't say that faster I/O is Digital Ocean's selling point - it's the price. If your bottleneck is I/O then you probably need more RAM, which Digital Ocean offers for 50% cheaper than Linode.
Regarding your other points, personally I'm not affected by the lack of IPv6 support (yet), and I don't know anybody else who is. I also think it's rich mentioning censorship and security considering Linode's history.
Between this, no IPV6 (in 2014, really?), censorship and the security fails, nobody should use Digital Ocean.